1. Field of the Invention
This invention relates to a novel antimicrobial filter and a filtration process employing said filter. More specifically, it relates to a water treatment process comprising filtering water through a bed of sand which is coated with antimicrobial chemicals that kill and prevent the growth of bacteria.
2. Prior Art
Antimicrobial metals have been known to be incorporated into paints and fibers for industrial or home applications. Organic quaternary ammonium silane has been shown to have anti-algae properties. The following patents show the use of silver, copper, and zinc in antimicrobial substances, and the use of organosilicon compounds.
U.S. Pat. No. 3,865,728 discloses an organosilicon compound coated on a fibrous substrate and then heated to 65-100 degrees C. The resulting product is used for control of algae in aquarium tanks.
U.S. Pat. No. 5,147,686 discloses an antimicrobial powder made by coating a titanium oxide substrate with antimicrobial metals including copper, zinc or alloys of Cuxe2x80x94Zn, Cuxe2x80x94Ag, Cuxe2x80x94Al, Cuxe2x80x94Sn or a combination of these metals. The composition is useful against various microorganisms such as E. Coli, Salmonella typhimurium, and others. The coated substrate is fired at 400 degrees C. The powder form of this product is intended to be incorporated into a resin.
U.S. Pat. No. 5,151,122 relates to an antibacterial ceramic material. Various ceramics such as zeolite or alumina or clay are described as being fired at temperatures as high as 1200-1300 degrees C. so as to lock in the absorbed antibacterial metals such as silver, copper, or zinc. The patent further suggests that the product can be added to a resin which can be molded into any shape.
U.S. Pat. No. 5,415,775 relates to an ultrafiltration membrane consisting of alumina and titanium dioxide which has been sintered at 1000-1500 degrees C. and then coated with metal oxide. The membrane exhibits anti-bacterial properties.
U.S. Pat. Nos. 5,618,762, 5,503,840, and 5,595,750 variously show Ag, Cu, Zn. Pt, Cd, Cr as antibacterial components including protective coatings.
None of the above patents addresses the problem of keeping water in reservoirs, cooling tower basins, public baths, and fish farms clear of harmful micro-organisms including algae or bacteria. In addition to its antimicrobial properties, the filter of the present invention is economical and shows high efficacy due to the small particle size structure of the sand which provides sufficient antimicrobial sites per unit volume and prolonged antimicrobial efficacy in flowing water due to strong adhesion of the antimicrobial components on the substrate, without any adverse environmental effects such as are encountered when chemical pesticides, bactericides or herbicides are used.
The object of this invention is to provide antimicrobial filters having coated thereon a metal composition such as silver or copper, or coated with an organic quaternary ammonium salt according to a specific process capable of eliminating harmful microbes such as E. coli, Salmonella typhimurium, and Saccharomycetes such as Saccharomyces cerevisiae, Candida albicans; Algae groups, such as Blue Green Algae, Brown Algae, and Green Algae, and Bacteria such as Chaetomium globosum, Penicillium funiculosum including Legionella pneumophila. Another object is to provide a process for treating water with inexpensive filter media which have been treated with the antimicrobial substances of this invention. Such filter media are easily handled and can be changed as frequently as necessary to eliminate harmful microbes. The method of filtering water can be carried out in commercially available equipment. The coated sand can be filled in a water container or encased in a container formed by a mesh screen whose mesh openings are smaller than the sand particles. The container can then be replaced when the chemical coating is spent. These objects of the invention will become apparent from the following description.
This embodiment of the invention is more economical than the honey-comb shaped substrate of applicant""s above-mentioned application. The coatings of sand with silver or copper may be based on the method described in the prior application except for the elimination of calcining aids in both organic and inorganic coatings.
In this invention, the sand treated with antibacterial substances removes suspended solids and eliminates bacteria and prevents their growth in the water.
The organic antimicrobial component is a quaternary ammonium salt having the formula: 
wherein m+n is 16 to 19, m is 1 to 6, and n is 13 to 17; or m+n is 20 to 23, m is 4 to 11 and n is 9 to 17 X is halogen; and Y is a hydrolyzable radical or hydroxy group. The inorganic antimicrobial components are silver or copper. These antimicrobial metal components are individually coated on sand with appropriate metals, and the coated sands are used as filter media either singly or in combination including inorganic-coated sand, to clean water.